Long-term administration of intranasal insulin improves peripheral glucose concentration in diabetic male rats

Introduction: Experiments in rodents and humans suggest that short-term intranasal insulin administration, which is known to reach the brain, does not affect peripheral glucose concentration under diabetic conditions. Methods: In this work, we provide evidence for the effect of intranasal insulin (10 IU/rat/day for 3 or 10 days) on serum insulin and glucose in streptozotocin-diabetic male rats using insulin measurements in the brain and periphery and a serum glucose assay 18 hours after three or ten days of nasal insulin administration. Results: Our findings revealed peripheral insulin increased and glucose level decreased in the diabetic male rats. Based on insulin kinetics, it seems that brain insulin directly or indirectly regulates serum insulin and glucose metabolism under diabetic conditions. Conclusion: Our results may suggest an insight into the therapeutic benefits of nasal insulin in diabetes.